The present invention relates to a process for the surface functionalisation of a polymeric substrate using diarylcarbenes as the reactive intermediates. The invention in particular relates to a process for the surface functionalisation, for example dyeing, of substrates such as cotton, a variety of plastics, polystyrene, nylon, controlled pore glass, silica, an ethylene polymer or polytetrafluoroethylene.
Dyestuffs which are used to colour natural and synthetic polymers, via covalent modification, most commonly rely upon the presence of highly reactive groups which have been coupled to the chromophoric species. Examples include the Procion and Gibacron range of dyes (which rely upon the reactivity of a chlorotriazinyl residue with nucleophilic residues on the substrate), the Remazol range of dyes (which rely on a vinylsulfonyl residue as a nucleophilic acceptor) and the Drimalon range of dyes (which contain an xcex1-chloroacetyl residue as the reactive species). Modifications of these reactive entities have been developed, leading to other related dye classes (e.g. the Drimarenes and Reactones, which use a tetrachloropyrimidine reactive unit, and the Primazin dyes, which use an acrylamide residue). Each of these reactive classes of dye have preferred substrates, although all contain aromatic or vinylic groups which are particularly activated towards nucleophilic attack by suitable functionality on the substrate. Development of this type of strategy still continues. However, in addition to the requirement for nucleophilic functionality on the substrate (which would usually be hydroxyl or amino groups), this approach generally requires vigorous conditions, such as high temperature or strongly basic media, for bond formation to occur.
An alternative technique whereby highly reactive carbene or nitrene spcies are generated from inert precursors under less harsh photolytic, and sometimes thermolytic, conditions has also been investigated for application to dyeing and other surface modifying processes of various natural and synthetic polymers. The chemistry of cargenes and nitrenes is well documented, and these reactive entities are known to form covalent bonds with many types of functional groups. The application of these species to the surface modification or organic solids using different approaches both for the generation of the required carbenes or nitrenes, and for their reaction with the solid surface has been reported. Interestingly, although nitrenes (often generated from an azide or sulfonylazide presursor under photolytic or thermolytic conditions) are more stable, and therefore less reactive, than their carbene analogues, they have been used much more widely for the dyeing of polymeric substrates.
French Patent No. 1 500 512 discloses allowing carbenes to come into contact with an organic solid. The preferred method for surface modification is to allow the volatilised carbene to come into contact with the polymer. Inherent in this approach, however, are limitations: only volatile (i.e. low molecular weight) carbenes, and those stable to relatively high temperatures, are applicable.
The application of carbenes generated from diazo compounds as suitable reactive dyes has been found to have important limitations, for example the ease of generation of the required diazo precursor (D. R. Braybrook et al., J. Photochem. Photobiol A: Chem, 1993, 70, 171) and the stability of the dye to the carbene generating process.
The present invention provides a process which may allow the surface functionalisation of materials which have hitherto been difficult to modify, for example glass or a variety of plastics. The process of the present invention may also allow greater flexibility than known processes in which a single carbene insertion step introduces the desired functionality. In addition, it is supposed that substrates which are dyed according to the process of the invention may exhibit superior wash-fastness to substrates dyed using existing processes due to a reduction in hydrolysable bonds on the surface of the substrate.
In a first aspect the present invention provides a process for the surface functionalisation of a polymeric substrate, which process comprises:
(a) contacting the substrate with a diarylcarbene precursor,
(b) generating a carbene reactive intermediate from the diarylcarbene precursor so that it reacts with the substrate to functionalise the surface, and
(c) further functionalizing the activated substrate obtained in step (b).
In another aspect of the present invention steps (b) and (c) are combined.
The substrate may be any natural or synthetic polymeric substrate which is capable of reaction with a carbene reactive intermediate generated from a diarylcarbene precursor. The molecular weight of the polymeric substrate may be selected according to the desired processability of the final product. Typically the substrate is cotton, plastic, polystyrene, nylon, controlled pore glass, silica, an ethylene polymer or polytetrafluoroethylene.
By xe2x80x9cdiarylcarbene precursorxe2x80x9d, as used herein, is meant a diaryl species capable of generating a carbene reactive intermediate under the reaction conditions. The diarylcarbene precursor must be such that the carbene reactive intermediate generated can react with the polymeric substrate and the activated substrate can be further functionalised.
Preferably the diarylcarbene precursor is a compound of formula I 
wherein
R is Ar1 or (CH2)mN(R1)(R2);
Ar1 is 
wherein Y is C1 to C4 alkoxy or N(R3)(R4),
R3 and R4, which may be the same or different, are C1 to C4 alkyl,
n is an integer of 0 to 3;
R1 is C1 to C4 alkyl;
R2 is phenyl;
m is an integer of 1 to 4; and
X is N2.
More preferably the diarylcarbene precursor is 4-([3,4-dimethoxyphenyl]oxymethyl)phenyl phenyl diazomethane 1, 4-([3-N,N-diethylaminophenyl]-oxymethyl)phenyl phenyl diazomeihane 2 or 4-([N-ethyl-N-phenyl-2-aminoethyl]oxymethyl)phenyl phenyl diazomethane 3.
Typically the diaryl diazomethane compounds are stable and may be stored at 0xc2x0 C. for extended periods.
Diarylcarbene precursors 1 and 2 may be prepared as shown in Scheme 1. 4-Bromomethylbenzophenone, which can be prepared according to D. D. Tanner et al., J. Org. Chem., 1980, 45, 5177, is first coupled with the desired aryl alcohol. The resulting benzophenone may be converted to the hydrazone by treatment in refluxing ethanol overnight, followed by removal of the solvent and extraction into dichloromethane. Oxidation of the hydrazone to the corresponding diazo diarylcarbene precursor may conveniently be performed with mercuric oxide in ether. 
Diarylcarbene precursor 3 may be similarly as shown in Scheme 2. 
By xe2x80x9ccarbene reactive intermediatexe2x80x9d, as used herein, is meant a reactive species comprising a formally divalent carbon atom. The carbene reactive intermediate is generated from the diarylcarbene precursor by treatment under conditions which result in an irreversible covalent reaction with the substrate. Generally the carbene is generated by heating the substrate and pre-adsorbed diazo compound, or by irradiation. Typically, the substrate is heated for the time required for decolourisation. In one embodiment of the present invention part of the surface of the substrate is activated by selective heating or irradiation, for example by photoactivation using a laser. This may allow the controlled and selective modification of a two-dimensional polymer surface and may be useful in two-dimensional data storage such as CD data storage.
The activated substrate obtained in step (b) is further functionalised. By xe2x80x9cfunctionalisexe2x80x9d, as used herein, is meant the introduction of a or another chemical functional group, which exhibits desirable physical or chemical properties, by irreversible covalent attachment. The activated substrate may be further functionalised by, for example, a dye, fluorescent brightener, UV-absorber, anti-static agent, flame retardant, surface finish, non-linear optical function, chelating function, electrically conducting function, magnetic function or polarising function.
The dye may be any suitable diazonium compound, for example a commercially available diazonium compound which may be selected to obtain the desired colour such as red, yellow, orange or blue. The colour may be altered in some cases by adjustment of pH of the final polymer sample by suitable treatment with acid or base. Examples of suitable diazonium compounds include those of formulae II, III or IV 
wherein
R5 and R6, which may be the same or different, are NO2 or SO3Na;
R7 and R8, which may be the same or different, are C1 to C4 alkoxy, preferably methoxy;
Ar2 is 
wherein R9 is C1 to C4 alkyl and q is an integer of 0 to 3, preferably 0; and
X is fluorine, chlorine, bromine or iodine.
The activated substrate may also be functionalised by, for example, introduction of a phthalocyanine functional group.
The process of the invention may find application in, for example, the dye industry, or combinatorial or polymer chemistry. More particularly the process of the present invention may find application in the preparation of immobilised catalysts, immobilised colours and dyes, photoelectric/solar cells, conducting (including photoelectric and semiconducting) polymers, magnetic polymers and optical recording and non-linear optical devices.
The process of the present invention may also be used in the preparation of biocidal or biostatic fabrics and plastics which have applications in, for example, water purification, medical and military clothing (where biocidal activity would help to minimise the transfer of infective agents or infections due to injury in the field) and surface anti-fouling of, for example, ship hulls, showers or tubing. The activated substrate obtained in step (b) of the process of the present invention may be functionalised by, for example, a chemical functional group comprising an antibiotic; a heavy metal such as silver, copper or zinc; a quaternary ammonium salt; a phosphonium salt; an oxidising agent such as an N-halamine or precursor thereof for example chloramine, chlorine, hydrogen peroxide or iodine; or a phenolic group. According to the process of the present invention the polymeric substrate may be, for example, a polymeric thread or a finished textile. The surface functionalised substrates prepared by the process of the present invention may be durable to repeated use and laundry, and may be regenerable. For example, the activated substrate obtained in step (b) may be functionalised using a urea hydroperoxide functional group which would be regenerable by treatment with hydrogen peroxide or an N-halamine functional group which would be regenerable with a chlorine solution such as hypochlorite bleach.
In a further aspect the present invention provides diarylcarbene precursors of formula 1 as defined above.